1. A boundary between two regions, countries, or territories that changes position over time due to political, military, or natural causes
The shifting border between the two nations has been a source of conflict for decades.
A fronteira móvel entre as duas nações tem sido uma fonte de conflito há décadas.
2. A demarcation line that is not fixed and moves or changes gradually
Climate change has created a shifting border for habitable zones.
A mudança climática criou uma fronteira móvel para as zonas habitáveis.